The first issue I'm running into is that bzero comes from sysdeps/ia64/bzero.S,
which declares bzero but not __bzero, which is referenced by a few RPC functions.
So in the end libc.so refuses to build with missing __bzero symbols.
After that there is another build failure, I'll paste the error message here:
/tmp/build/libc_pic.os: In function `faccessat':
(.text+0x130952): undefined reference to `fstatat64'
collect2: ld returned 1 exit status
make[1]: *** [/tmp/build/libc.so] Error 1
This should be self-explanatory.